Re: [Libguestfs] [PATCH] [v2] WIP: ddrescue mapfile filter

Oh cool, this sounds very similar to the existing extentlist plugin, but with a difference that extentlist uses the input to decide which portions of the file are advertised as sparse, while this one uses which portions of the file cause EIO errors during read. Is it worth trying to combine the two concepts into one filter, or do we want to keep it orthogonal as two separate filters? Can we teach both filters to reuse common code for parsing extent lists in different formats (the extentlist format is the same format documented by the nbdkit-sh-plugin .extents; yours is the ddrescue format, I am also interested in the 'qemu-img map --output=json' format)? In fact, if we introduce a common library for extent list parsing, teaching nbdkit-sh-plugin to accept all formats might be useful.

Or even make it configurable (via another .config knob) whether bad blocks read as zero or cause EIO.